Digital products, such as computer, PDAs, MP3s, industrial computers, etc., are more and more popular in the current human life, however reading devices are important I/O devices. Currently, there are a variety of memory cards, such as compact flash cards (CF cards, smart cards (SM cards), MMC cards (multi media cards), security digital cards (SD cards), memory stick card (MS cards), magic gate cards (MG cards), etc., are used commonly by people. General, the memory cards can not match the specification of a computer interface since the computer interface is designed for only a few kinds of memory cards. Thereby, adaptors are developed to be installed between the interfaces and the memory cards. The data can be transferred between the interface of the computer and the memory card. However in this prior art the transmission speed is low and adaptor are dependent on memory cards. Thereby, the users must prepare different kinds of adaptors for matching the kinds of the memory cards. It is inconvenient and the price is high.